Energetic materials are used in a variety of applications. They may be used as explosives, pyrotechnic applications, as propellants and as fuels. In a number of instances, it may be desirable for energetic materials to provide a structural function as well. However, many types of energetic materials, including most thermitic type reactive materials, are brittle or have little strength. Various attempts have been made to provide an energetic material that may be used to form structural or load bearing components. For example, U.S. Pat. No. 8,007,607, entitled COMBUSTIBLE STRUCTURAL COMPOSITES AND METHODS OF FORMING COMBUSTIBLE STRUCTURAL COMPOSITES, describes a combustible material that includes structural reinforcing fibers such that the resulting material is capable of carrying substantial structural design loads.
In addition to issues relating to brittleness and strength, numerous energetic materials, such as thermitic type materials, can be static sensitive. The static sensitivity of such materials may create a hazard of the material being ignited or combusted at an unanticipated time, making the materials unsuitable for a variety of applications or, at least, requiring substantial fail safe mechanisms or procedures to prevent any inadvertent ignition or combustion.
Thin film energetic composites are also a growing area of research because of their potential for providing localized power generation in miniaturized applications. However, the development of both materials and manufacturing processes amenable to producing such thin film energetic materials has not been without difficulty. One synthesis approach that has combined fuel and oxidizer powders with a binder and solvent system includes forming a very thin film (e.g., approximately 100 microns or less). This technique has been utilized previously in the manufacture of capacitors and batteries as well as for prototype fabrication of laminated ceramic components. Early reporting of blade casting of an energetic material was directed to thermal battery applications and utilized magnesium (Mg) and manganese dioxide (MnO2) as the energetic composite combined with various binder-solvent systems. It has been shown that polyvinylidene fluoride (PVDF) and n-methylpyrrolidone (NMP) may be an effective fluoropolymer binder and organic solvent combination because they provide relative homogeneity (i.e., less settling and segregation of particles) and generally lead to improved combustion. In one example, such a material was synthesized and a film measuring 60 mm×6 mm and 100 micron thick were deposited and adhered to substrates. The films produced calorific output on the order of 4 kJ/g and energy propagation on the order of 0.14 m/s, suitable for thermal battery applications.
It is a continued desire in the industry to provide new materials and processes that enable energetic materials to be used in new applications and environments including use as self-supporting structural components.